1. Field of the Invention
The present invention relates to a resist composition having performances high in sensitivity and high in resolution against an electromagnetic waves such as an ultraviolet light, a far ultraviolet light, a vacuum ultraviolet light, an X-ray, and the like and a electrically charged particle such as an electron beam, an ion beam, and the like, and high in safety against environment, a fabricating method for patterned substrate by using the resist composition, and also the device having a substrate fabricated by the fabricating method.
2. Related Background Art
In recent years, according to a high density and high speed semiconductor integrated circuit, miniaturization and integration of the integrated circuits are being progressed than the past. Large capacity memory devices for these integrated circuits is transcribed from a mask to a semiconductor substrate by using the light belonging to near ultraviolet light and far ultraviolet light. In these ranges of light wavelength, a processible line width of a semiconductor device is coming close to a limit. Therefore, it is necessary to promote to use a short wavelength for an exposing light. In recent years, an ArF excimer laser and a F2 laser are being used as the light source for exposure in order to develop a lithography technology.
In accordance to using such short wavelength as the exposure wavelength, a severe problem arises, for example, a transmittance of the resist against the exposure light lowers to cause deterioration of resolution performance of a pattern. Particularly in light lithography using the ArF excimer laser as the light source, novolac resin and polyvinyl phenol, which is used in a conventional resist and has an aromatic ring in a structure thereof, are very difficult to be used in view of light transmittance due to a high light absorbance by this aromatic ring. On the other hand, it has been known that light transmittance of the exposure light can be improved largely by using an aliphatic polymer. However, as a rule, the resist using the aliphatic polymer is inferior in resistance against dry etching at processing of the substrate following pattern formation. Hence, the resist, which is prepared by using a polymer having an alicyclic group in a polymer side chain, has been developed. For example, the resist prepared by using norbonen-methacrylate copolymer and adamanthyl methacrylate. Resists prepared by these polymers have been described on, for example, Japanese Patent Application Laid-Open No. 5-80515 and Japanese Patent Application Laid-Open No. 5-265212. However, the polymer having the alicyclic group is generally difficult to be fabricated at low cost and low in solubility in a solvent and a developer to cause to be difficult to yield the resist having a high performance. In addition, concerning a material itself for the resist, making a low load on nature environment is required.
On the other hand, the material based on cellulose shows high transmittance in the short wavelength region of the ArF excimer laser and the like and thus, is preferable as the resist. For example, in Japanese Patent Application Laid-Open No. 6-34412, a polymer compound, which is prepared by substituting at least part of a hydroxyl group of cellulose to a protecting group, is proposed to use as the resist. In addition, in Japanese Patent Application Laid-Open No. 10-213903, a proposal is made for a positive type resist compound made of the cellulose resin having an acid functional group, an acidic acrylic resin, and a photo acid generator. However, the polymer prepared by simple substitution of the hydroxyl group of cellulose is difficult to satisfy control of solubility in a solvent, which is used for solubilization of the resist, and solubility of the polymer dissolved in an alkali aqueous solution, which is used for development, and resist performance, at the same time. Therefore, a high performance resist is difficult to be obtained.